1. Field of the Invention
This invention relates to valves and, in certain embodiments to valves used in wellbore operations. In certain particular aspects this invention relates to equipment for well cementing operations, to float valves and to float equipment, and also to auto-fill flow valves useful in such operations.
2. Description of Related Art
Flow control valves are commonly used in wellbore cementing operations. Typically valves used in equipment employed in such operations are kept in float shoes or float collars of casing as the casing is run into the well to automatically fill the casing from the bottom at a predetermined rate to save rig time expended in manually filling a casing string from the surface as it is being run into the borehole and to reduce the amount of fluid flowing up the annulus between the casing's exterior and the wellbore's interior, thereby reducing surge pressure at a float shoe. Certain prior art floating equipment has some type of sacrificial mechanical part for maintaining the valve in an open position, e.g. shear plates, shear pins, extrusion rings, sliding sleeves, or tension collars. These mechanical items have a calculated strength so that the valve is held open until they move or are broken.
Certain prior art automatic fill float shoes or float collars require a ball or plug to be dropped through the casing string to seal in the valve mechanism of the float shoe or float collar and to seal off the valve mechanism so that pressure applied thereto releases the locked open check valve through shearing or deformation of a sacrificial mechanical part. With such valves there may be a time delay during which the ball or plug has to fall through the fluid in the casing.
Related art includes the valves and cementing equipment shown in the following publications of Weatherford International Incorporated (owner of the assignee of this invention): "Cementing Program," 1986; "General Services And Products Catalog," 1990-91; "Weatherford Cementation Products," 1990; "Stage Tool 620," 1990; "AF-SURE-SEAL Technical Bulletin HOU 123-001," 1986; "Model 820 Float Valves Technical Bulletin HOU 115-001," 1984; "Model 457 Float Valves Technical Bulletin HOU 114- 001," 1984; and "Conventional and Specialized Float Equipment," 1985 (which are incorporated fully herein for all purposes and copies of which are submitted with the application for this patent).